The present invention pertains to an apparatus for providing more efficient extraction of solubles from ground coffee in a drip filtration brewer.
In a drip filtration system for brewing coffee, the ground coffee is placed into a container such as a brew basket holding a filter and hot water is passed through the brew basket, extracting flavoring solubles from the coffee grounds in a single pass into a decanter positioned below. Because a major and consistent goal of a commercially acceptable coffee brewer is to provide a consistently good tasting cup of coffee, manufacturers continuously strive to further develop brewing equipment that addresses the discriminating tastes of the consumers. While there are many factors that contribute to the make up of a good tasting brew, it has long been recognized that the major contributors to the make up of this good taste are the concentration of the flavoring solubles in the brew and the percentage yield of solubles gained during the extraction process. Too high of a concentration of flavoring solubles is perceived as being strong coffee while too small of a concentration tastes weak to the consumer. An inefficient extraction may result in a coffee brew considered to taste strange such as grassy or peanut-like while over-extraction results in a bitter brew. There are various types of solubles that provide flavoring to the resulting beverage and they are extracted at different rates. That is, certain solubles come out of solution readily from the grounds when contacted by the hot water while others require additional contact time. Additionally, certain chemical reactions are promoted when the hot water is passing through the grounds and can continue after the brew has been made under certain circumstances such as when the brew is maintained at or above certain temperatures. The bitter taste that is often objected to by consumers may be due to over-extraction and/or over-cooking of the coffee once made. The graph of FIG. 10 illustrates this alteration of taste at various concentration and extraction percentages. Thus, there is a desired balance of these percentages that provide a coffee brew which is perceived as having an optimum taste as shown by the areas of the graph depicted by the character numeral 100. On one side of area 100, the coffee flavor is considered "underdeveloped" while on the other side the coffee flavor is said to be "overdeveloped". Above the area 100, signifying a high level of concentration, the coffee is said to be "too strong" and below is considered "too weak".
Applicant, after careful examination of the brewers of the prior art, has determined that such brewers tend to provide an inconsistent extraction of coffee solubles, often leading to the undesired "under developed" taste. Some of the ground coffee positioned in the brew basket is over extracted while the remainder is likely to be under extracted. As will be discussed below, this over and under extraction result can be demonstrated by permitting the grounds to dry following the pass-through of the hot water. The dried grounds show a visible and distinct variation from a lighter to darker color from the center to the periphery regions which indicates that a greater extraction of the solubles occurs at the center than at the outer regions. Applicant has postulated that during brewing the inner portion of the basket is showered with hot water and that some of the grounds in the outer ring float in hot water and are not extracted. Realizing the importance of this finding, applicant set out to construct a brewer in which the extraction was consistent through out the brew basket during the brewing process.